class OpenSSL::BN

def to_ssh

required by the SSH2 protocol.
Converts a BN object to a string. The format used is that which is 
def to_ssh
  if zero?
    return [0].pack("N")
  else
    buf = to_s(2)
    if buf.getbyte(0)[7] == 1
      return [buf.length + 1, 0, buf].pack("NCA*")
    else
      return [buf.length, buf].pack("NA*")
    end
  end
end